Technical Field
This disclosure relates to a scanning line adjuster, an optical scanner incorporating the scanning line adjuster, and an image forming apparatus incorporating the optical scanner.
Related Art
Various types of electrophotographic image forming apparatuses include copiers, printers, facsimile machines, or multifunction machines having two or more of copying, printing, scanning, facsimile, plotter, and other capabilities. Such image forming apparatuses usually include an optical scanner for scanning a writing light beam onto a latent image bearer that is a scanned target object. The optical scanner typically includes a polygon mirror to deflect the writing light beam emitted by a light source, and optical elements such as long lens to pass the writing light beam deflected by the polygon mirror and form an image on a surface of the latent image bearer.
Specifically, for example, an optical scanner includes a scanning line adjuster to adjust inclination of a scanning line by adjusting an attitude of a long lens. The scanning line adjuster includes a long lens unit that functions as an optical unit provided with a long lens and a bracket to hold the long lens. The long lens unit is supported by an optical housing and is rotatable along an optical axis orientation around a center in a longitudinal direction of the long lens. The optical housing has a positioning face that functions as a positioning member to contact a longitudinal end of the long lens unit from the optical axis orientation and position the long lens unit along the optical axis orientation. A leaf spring is attached to the optical housing to press the positioning face such that the longitudinal end of the long lens unit faces the positioning face with the long lens unit interposed therebetween. The scanning line adjuster includes an attitude changer that changes an attitude of the long lens unit by pressing the other longitudinal end of the long lens unit in a sub-scanning direction, that is, a direction perpendicular to both the optical axis orientation and a longitudinal direction of the long lens and rotating the long lens unit about the optical axis.
If the scanning line scanned on the surface of the latent image bearer is inclined, the attitude changer presses the other longitudinal end of the long lens unit in the sub-scanning direction to rotate the long lens unit about the optical axis. As the long lens unit rotates, the inclination of the scanning line on the surface of the latent image bearer is corrected.
In the above-described optical scanner, when the attitude of the long lens unit is adjusted by rotating the long lens unit about the optical axis, the one longitudinal end of the long lens unit moves along the positioning face of the optical housing in a direction opposite the direction in which the attitude changer presses the long lens unit. At this time, however, if the static friction generated between the positioning face and the optical housing is large, movement of the one longitudinal end of the long lens unit along the positioning face is hindered by the static friction, and therefore the opposed end side in the longitudinal direction of the long lens moves by a given amount as pressed by the attitude changer. As a result, after completion of inclination adjustment of a scanning line, the long lens unit is curved in a bow shape, and accordingly, it is likely that a scanning line on a surface of the latent image bearer bends.